Most organisms respond to stimuli in their environment by movement (taxis) toward or away from the stimulus; yet the molecular mechanism of taxis is poorly understood in any organism. The research proposed here will explore bacterial behavior, especially chemotaxis (movement toward or away from chemicals) in Bacillus subtilis and phototaxis (movement toward light) and chemotaxis in Rhodospirillum rubrum. The ultimate objective is to describe the behavior in molecular terms. More immediately, we ask such questions as the following: What is the mechanism by which information is transmitted from receptors to flagella? How do receptors--photoreceptors or chemoreceptors--generate this signal? The immediate experimental objectives of work for this coming year are the following: for B. subtilis: 1) isolation and characterization of alanine and proline chemoreceptors; 2) characterization of specificities of amino acid chemoreceptors; 3) biochemical study of role of methionine in chemotaxis by B. subtilis; 4) exploration of mechanism of action of uncouplers of oxidative phosphorylation since they are repellents; for R. rubrum: 5) development of light trap assay for phototaxis and isolation of mutants for phototaxis. BIBLIOGRAPHIC REFERENCES: Ordal, G. W., and D. J. Goldman. Chemotaxis away from uncouplers of oxidative phosphorylation in Bacillus subtilis. Science 189: 802-805 (1975).